A drag reducer is a composition capable of substantially reducing friction loss associated with the turbulent flow of a fluid through a conduit. Where fluids are transported over long distances, such as in oil and other hydrocarbon liquid pipelines, these friction losses result in inefficiencies that increase equipment and operations costs. Ultra-high molecular weight polymers are known to function well as drag reducers, particularly in hydrocarbon liquids. In general, drag reduction depends in part upon the molecular weight of the polymer additive and its ability to dissolve in the hydrocarbon under turbulent flow. Effective drag-reducing polymers typically have molecular weights in excess of five million.
In the past, it has been proposed that drag reducers comprising polymeric latex emulsions can be used to reduce friction loss associated with turbulent fluid flow through a conduit. The use of polymeric latex emulsion drag reducers has most commonly been proposed for application to the flow of hydrocarbon streams (e.g., crude oil, gasoline, diesel fuel, etc.) through pipelines. In order to be most effective, the drag reducer must be dissolved in the hydrocarbon stream.
Currently, a number of different commercial approaches are being taken to address the problem of preparing, dissolving, transporting and using such drag reducing polymers. A common commercial method is to prepare the polymer in dilute solutions in an inert solvent such as kerosene or other solvating material. This method utilizes a solution of high molecular weight polymer suitable for use as a drag reducing agent when produced by polymerization of alpha olefins in a hydrocarbon solvent. The entire mixture, containing polyolefin, solvent, and catalyst particles is used without separation to form dilute solutions of the polymer in crude oil or finished hydrocarbons.
Another current commercial approach to drag reduction is to polymerize alpha olefins in bulk form, mill the bulk polymer into small (50μ to 500μ) particles, and then suspend the particles in an aqueous or other (non-solvent) liquid medium. This method allows for much higher levels of active drag reducing polymer in the final product (up to about 25%).
Yet another method is to polymerize monomers with slight water solubility using emulsion polymerization. This method has the advantage that suspensions containing high levels of active drag reduction polymer (up to 45%) can be prepared. Unfortunately, the types of monomers that can be used in emulsion polymerization are not always the best choices for making drag reducing polymers for use in hydrocarbon fluids (crude oil, gasoline, and diesel fuel).
The use of miniemulsion polymerization techniques for the production of drag recuing polymer prepared with very water insoluble monomers solves the problem of using the best, water insoluble monomers for the production of drag reducers for use in hydrocarbon liquids.